Hand-held apparatus and method

ABSTRACT

There is disclosed a gas sampling apparatus adapted for use in a hand-held gas sensing device having at least one gas sensor, the apparatus comprising: a gas inlet; a gas conductor for conducting gas from the gas inlet to the sensor or sensors; a gas outlet; a gas conductor for conducting gas from the sensor or sensors to the gas outlet; and a vacuum containment enclosing an inner region having a pressure below atmospheric pressure and adapted for connection to the gas outlet so that a flow of gas is developed from the gas inlet to the vacuum containment.

RELATED APPLICATION DATA

[0001] This application is a divisional of copending patent applicationU.S. Ser. No. 09/462,304, filed Mar. 13, 2000, now U.S. Pat. No.6,431,016, to issue Aug. 13, 2002, which claims priority fromPCT/GB98/01938, filed on Jul. 1, 1998, which claims priority fromGB9714166.7, filed Jul. 5, 1997.

BACKGROUND OF THE INVENTION

[0002] This invention relates to apparatus and methods for gas sampling,with particular reference to gas sampling in hand-held portable gassensing devices.

[0003] Devices which can detect a range of gases (so-called “electronicnoses”) have recently become commercially available. Such devicestypically comprise an array of individual gas sensing elements, theelements having broad and overlapping sensitivities. The identity of agas is established by reference to the pattern of response across thearray of sensors (see, for example, Gardner, J. W. and Bartlett, P. N.,Sensors and Actuators B, 18-19 (1994) pages 211-220; Persaud, K. C.;Bartlett, J. G. and Pelosi, P., in “Robots and Biological Systems:Toward a new bionics?,” Eds. Dario, P., Sandini, G. and Aebisher, P.,NATO ASI Series F: Computer and Systems Sciences 102 (1993) 579 andreferences therein).

[0004] Electronic noses have to date generally comprised bench-topunits, usually interfaced to a personal computer which performs patternrecognition functions and data processing. Such devices are perfectlyconvenient for use in a laboratory, but are not portable and thereforenot suitable for use in the field. It is likely that the next generationof electronic noses will include portable, hand-held devices. Oneproblem with the production of a practical, hand-held electronic nose isthe gas sampling system. Conventional bench-top electronic noses utilizesmall pumps to draw a stream of gas across the gas sensor array. It isless desirable to employ such an approach in a hand-held device, becauseof the additional requirements placed upon the battery power source,with consequential and unacceptable increases in the weight and volumeof the instrument.

[0005] The present invention addresses the above-named problem.

SUMMARY OF THE INVENTION

[0006] Although primarily directed towards electronic noses, the presentinvention has within its scope other hand-held gas sensing devices,including gas specific, single sensor devices.

[0007] For the avoidance of doubt, the term “gas” is understood toembrace any ambient atmosphere, which might comprise a mixture of gasesand/or vapors.

[0008] According to a first aspect of the invention, there is provided agas sampling apparatus adapted for use in a hand-held gas sensing devicehaving at least one gas sensor, the apparatus comprising:

[0009] gas inlet means;

[0010] gas conducting means for conducting gas from said gas inlet meansto the sensor or sensors;

[0011] gas outlet means;

[0012] gas conducting means for conducting gas from the sensor orsensors to the gas outlet means; and

[0013] vacuum containment means enclosing an inner region having apressure below atmospheric pressure and adapted for connection to thegas outlet means so that a flow of gas is developed from the gas inletmeans to the vacuum containment means.

[0014] The apparatus may further comprise pressurized wash gascontainment means containing a wash gas and adapted for connection tothe gas outlet means so that a flow of wash gas is developed across thegas sensor or sensors.

[0015] The apparatus may further comprise pressurized reference gascontainment means containing a reference gas and adapted for connectionto the gas outlet means so that a flow of reference gas is developedacross the gas sensor or sensors.

[0016] The gas outlet means and/or the gas inlet means may comprisevalve means.

[0017] The vacuum containment means may comprise valve means.

[0018] The apparatus may further comprise gas flow constriction means.

[0019] According to a second aspect of the invention there is provided amethod for sampling gas in a hand-held gas sensing device having atleast one gas sensor comprising the steps of:

[0020] providing apparatus according to the first aspect of theinvention; and

[0021] connecting the vacuum containment means to the gas outlet meansso that a flow of gas is developed from the gas inlet means to thevacuum containment means.

[0022] The step of connecting the vacuum containment means to the gasoutlet means may be preceded by the steps of:

[0023] connecting pressurized reference gas containment means containinga reference gas to said gas outlet means so that a flow of reference gasis developed across the gas sensor or sensors.

[0024] This step comprises a “reference cycle.”

[0025] The step of connecting the pressurized reference gas containmentmeans may be preceded by the step of:

[0026] connecting pressurized wash gas containment means containing awash gas to said gas outlet means so that the flow of wash gas isdeveloped across the gas sensor or sensors.

[0027] This step comprises a “wash” cycle.

[0028] The method may further comprise the steps of gas tightly sealingthe vacuum containment means; detaching same from the gas outlet means;and transporting said vacuum containment means to secondary analysismeans for further analysis of the sampled gas.

[0029] The foregoing and other objects, features and advantages of theinvention will become more readily apparent from the following detaileddescription of a preferred embodiment of the invention which proceedswith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawing is a schematic diagram of a gas sampling apparatus.

DETAILED DESCRIPTION

[0031] Each embodiment of apparatuses and methods in accordance with theinvention will now be described with reference to the accompanyingdrawing, which is a schematic diagram of a gas sampling apparatus.

[0032] The drawing shows gas sampling apparatus 10 adapted for use in ahand-held gas sensing device 12 having at least one gas sensor 14, theapparatus 10 comprising:

[0033] gas inlet means 16;

[0034] gas conducting means 18 for conducting gas from said gas inletmeans 16 to the sensors 14;

[0035] gas outlet means 20;

[0036] gas conducting means 22 for conducting gas from the sensors 14 tothe gas outlet means 20; and

[0037] vacuum containment means 24 enclosing an inner region having apressure below atmospheric pressure and adapted for connection to thegas outlet means 20 so that a flow of gas is developed from the gasinlet means 16 to the vacuum containment means 24.

[0038] In the present example, the hand-held gas sensing device 12 is anelectronic nose having an array of sensors 14, although other sorts ofhand-held gas sensing devices, including single sensor devices, arewithin the scope of the invention. The vacuum containment means 24 maycomprise any suitable vacuum container, such as a vacuum flask having asteel body and an inner sleeve (which bounds the inner region)comprising, for example, glass or PTFE. The gas conducting means 18, 22may comprise tubing, or, possibly, suitable conduits formed in the bodyof the device 12.

[0039] Prior to sampling the gas to be detected, there are certain otherfunctions which are advantageously performed, namely a wash cycle and areference cycle. The present invention provides means for convenientlyperforming these cycles in a hand-held instrument. Thus, the apparatus10 further comprises pressurized inert gas containment means 26containing a wash gas and adapted for connection to the gas outlet means20 so that a flow of wash gas is developed across the gas sensors 14.The wash gas, which might comprise a water/butanol mixture is apressurized inert gas, such as a noble gas, washes the gas sensors 14.The gas flow path is conveniently (although not necessarily) the reverseof the gas flow path when the gas to be detected is sampled.

[0040] In order to perform the reference cycles, the apparatus 10further comprises pressurized reference gas containment means 28containing a reference gas and adapted for connection to the gas outletmeans 20 so that a flow of reference gas is developed across the gassensors 14. Since the sample atmosphere is likely to be humid, asuitable reference gas could be compressed air at a defined humidity.The use of a reference gas provides a response baseline for the gassensors 14. The subsequently sampled gas may be detected by responsevariations away from the baseline response established by the referencecycle.

[0041] Preferably, the gas inlet means 16 and the gas outlet means 20comprise valve means 30, 32 operable to selectively open and close theinlet and outlet means 16, 20. Clearly, such is highly desirable if awash cycle is employed. The valves means 30, 32 can be manuallycontrolled, or electronically actuated as part of the automaticoperating protocol of the device 12. Another possibility is a two-wayvalve which mechanically operates when a given pressure differential isexceeded, irrespective of which side of the valve is at the higherpressure. Such a valve would be compatible with the reversal in thedirection of gas flow which occurs between gas sampling and the wash andreference cycles. The gas inlet means 16 may also comprise an air filterto prevent particulate matter entering the device 12. Suitably shapedtubular probes may be attached to the gas inlet means in order to samplegas from otherwise inaccessible regions.

[0042] Advantageously, the vacuum containment means 24 comprises valvemeans 34. The advantage of such an approach is that after gas has beensampled by the gas sensors 14, the valve means 34 can be closed, and thevacuum containment means 24 detached from the gas outlet means 20 andtransported to secondary analysis means for further analysis of thesampled gas. Such secondary analysis means can be a laboratory baseddevice such as GC/MS, and might be used simply to confirm the resultsproduced by the as sensing device 12 or for providing additionalinformation.

[0043] It is quite possible to provide the pressurized wash gascontainment means 26 and the pressurized reference gas containment means28 with valves. Alternatively, the gas outlet means 20 might beprovided, for example, with puncturing teeth so that connection ofeither the wash gas containment means 26 or reference gas containmentmeans 28 to the gas outlet means 20 punches an aperture in the former,in much the same way that portable, outdoor gas stoves operate.

[0044] The flow of gas into the vacuum containment means 24 can becontrolled by suitable flow constriction means, which might comprise oneof the valve means 30, 32, 34 or a needle valve, or a mass flowcontroller.

[0045] The vacuum 24, pressurized wash gas 26 and pressurized referencegas 28 containment means may be conveniently and portably stored in abag or a pouch. In use, the pressurized wash gas containment means 26 isconnected to the gas outlet means 20, normally directly after theprevious measurement. Valve means 30, 32 are opened so that wash gasflows from the pressurized containment means across the gas sensors 14and exits from the gas inlet means 16, thereby washing the samplingapparatus in general, and the sensors 14 in particular. Next, the washgas containment means 26 is removed and pressurized reference gascontainment means 28 is connected in the same manner. The process isrepeated, in order to obtain a reference response from the gas sensors14 (although further washing may be performed during this process). Thereference gas containment means 28 is then removed from the gas outletmeans 20, the vacuum containment means 24 connected thereto, and thevalve means 30, 32, 34 are opened so that a flow of gas is drawn throughthe gas inlet means 16, across the gas sensors 14 and into the vacuumcontainment means 24. The valve means 30, 32, 34 are then closed,whereupon the vacuum containment means 24 is detached from gas outletmeans 24. The vacuum containment means 24 now contains an atmosphere ofsampled gas which can be transported to a laboratory for furtheranalysis.

[0046] Having described and illustrated the principles of the inventionin a preferred embodiment thereof, it should be apparent that theinvention can be modified in arrangement and detail without departingfrom such principles. I claim all modifications and variation comingwithin the spirit and scope of the following claims.

1. A hand-held sensing apparatus comprising: a housing; a sensor modulemounted in the housing and including at least two sensors that provide adistinct response to a particular test sample; a sample chamber definedby one or both of the housing and the sensor module, the sample chamberincorporating an inlet port and an outlet port, wherein the at least twosensors are mounted within or adjacent to the sample chamber; andanalysis means configured to analyze a particular response from the atleast two sensors and produce an analytic result.
 2. A method foranalyzing a gas test sample using a hand-held gas analyzer, comprising:providing a sensor array which includes at least two sensors in a samplechamber within a hand-holdable housing; introducing the gas test sampleinto the sample chamber via an inlet port; contacting the gas testsample to the at least two sensors in the sample chamber; generating aresponse by the at least two sensors; and analyzing the response toproduce an analytic result of the gas test sample.